Amorphous alloy stents

ABSTRACT

Stents made of bulk-solidifying amorphous alloys and methods of making such stents are provided.

FIELD OF THE INVENTION

The present invention relates to stents made of bulk-solidifyingamorphous alloys and methods of making such articles.

BACKGROUND OF THE INVENTION

Stents are small and expandable tubulur members, which are inserted intoclogged blood vessels to restore proper blood flow, or to treat otherdamaged passageways or lumens in the body, like bronchi or theesophagus. In turn, placing a stent implant (stenting) is often acatheter-based procedure. In the example of vascular stenting, acatheter is used to place a stent into a diseased artery to maintain thevessel patency after balloon angioplasty. In another application,covered stents (called stent-grafts) are also used to treat aneurysms,including abdominal aortic aneurysms. In a stent-graft procedure, thephysician prevents blood from filling the aneurysm (bulge in artery) byplacing a stent graft at the aneurismal site.

Generally there are two classes of stents: balloon-expanded stents, andself-expanding stents. Balloon expanded stents are initially smallenough to enter the body lumen easily and are fitted over a collapsedballoon. The stent is then expanded through plastic deformation as theballoon is inflated. After inflation, the stent is in tightapproximation to the lumen wall. The specific design of the stent struts(mesh segments) is optimized to provide a flexible, unexpanded structurethat can track through the body cavities during insertion, and a patentlumen after expansion. Self-expanding stents are naturally sized fortight fit in the target lumen, but held in a compressed state duringdelivery through the body lumens to the target site. Once theself-expanding stent is located at the target lumen site, then the stentis release and allowed to spring back to its natural, expanded size.Design considerations similar to those followed with balloon-expandedstents are used in the design of a self-expanding stent. Theself-expanding stent must track through the vasculature in the collapsedstate and fit the lumen when expanded to provide patency. The struts ofthe self-expanding are designed to elastically deform during compressionand return to a predetermined final shape. Those can be made of awire-mesh or a specially designed pattern of slots or apertures.

Specific stent strut structures include wire-mesh, specially designedpattern of slots or apertures, coiled springs, helical wound springcoil, expanding forms in a zig-zag pattern, diamond shaped, rectangularshaped, and other mesh and non-mesh designs. Stents come in differentsizes and designs depending on the many factors. Some of the factorsinclude: 1) the size of the artery in consideration; 2) where theblockage is located; 3) the extent of the blockage; 4) the extent ofblockage in other arteries; 5) the strength of the heart muscle; and 6)the interaction of the implanted stent with the vascular (or targetlumen) physiology.

Despite the number of different considerations used in the designing astent, the variety of materials used is quite limited. For example,stainless steel is the most common metal used for stents although,nitinol is also gaining wide-spread acceptance.

The quality of stent's function can be measured in terms of acuteperformance and chronic performance. Acutely, the stent keeps the lumenwall from recoiling after balloon expansion, and keeps dissected flapsfrom causing acute closure at the angioplasty site. Chronic performanceof a stent is gauged by the degree of restenosis (re-blockage) in thetreated lumen. Restenosis is considered to be a proliferative cellularresponse to the injury caused during angioplasty and stent implantation.Approximately 20 percent of stents close (restenose) within six monthsof placement.

Improving stent performance can be measured against several othercriteria: 1) designing smaller diameter stents (less than 2.5millimeters) for smaller vessels; 2) custom-designing stents for anoptimal fit; 3) designing stents for multiple sites within the sameartery (including stents with side branches); and 4) providing effectivecoating of stents with anticoagulants and antiproliferation agents.

Unfortunately, current materials used in stents are not readilyadaptable to many of these desired improvements. The limitations of thecurrent stent materials include both limited fabricability, andnon-optimal physical and mechanical properties. For example, themechanical properties of stainless steel and nitinol depend on thehistory of thermo-mechanical process history. As such, variousfabrication and finishing steps can result in inconsistent or inferiorphysical and mechanical properties. Furthermore, the physical andmechanical properties of current materials are not generally sufficientfor the development of new novel stent designs, such as stents havingdiameters less than 2.5 mm.

Accordingly, a need exists for a new class of materials to address thematerial and fabrication deficiencies of current materials as well as toprovide options and tailorable properties for the various demands ofstents.

SUMMARY OF THE INVENTION

The current invention is directed to stents made of bulk-solidifyingamorphous alloys and methods of making such stents.

In one embodiment of the invention, the stent is made of abulk-solidifying amorphous alloy. In one preferred embodiment of theinvention, the stent is made of Zr/Ti base bulk-solidifying amorphousalloy.

In another embodiment of the invention, the stent has a hexagonal orround cross-section.

In still another embodiment of the invention, the stent is a coiledspring, helical wound spring coil, zig-zag pattern, diamond shaped, andother mesh and non-mesh designs.

In yet another embodiment of the invention, the wall of the stent hasmultiple aperture openings.

In still yet another embodiment of the invention, the stent is braidedto improve flexibility in longitudinal direction and strength in radialdirection.

In still yet another embodiment of the invention, the percentage ofvessel covered by the stent is between 9 to 20%.

In still yet another embodiment of the invention, the percentage ofvessel covered by the stent is more than 80%.

In still yet another embodiment of the invention, the stent is porous inthe form of wire, tube or metal sheet, used for treating vasculaturedisease by delivering medication to the implant site.

In still yet another embodiment of the invention, the bulk solidifyingamorphous alloy component of the stent is coated with anticoagulants(preventing the formation of a blood clot in the stent) and/orchemotherapeutic drugs to potentially minimize restenosis.

In still yet another embodiment of the invention, the stent contains atleast one drug is loaded into the pores.

In still yet another embodiment of the invention, the cover tubes isporous and contains medicine or other substances to improve theperformance of the stent.

In still yet another embodiment of the invention, the stent is a coveredstent in which the stent is covered with a tube or multiple tubes madeof metal, biodegradable material, plastic or other material.

In still yet another embodiment of the invention, the stent is a coveredstent in which the stent is covered with a tube or multiple tubes madeof metal, biodegradable material, plastic or other material and whichare impregnated with an anticoagulant and/or chemotherapeutic drugs topotentially minimize restenosis.

In still yet another embodiment of the invention, the stents are coatedwith radioactive material, or other bioactive substances to improve theperformance of the stent.

In still yet another embodiment of the invention, the stent is made upof two or more tubular stent segments which may be deployed together soto produce a single axial length by a provision of overlapping orabutting areas. In such an embodiment the cross section of the stent mayvary according to the blood vessel.

In still yet another embodiment of the invention, the stent is to beself-expanding and therefore does not need a separate angioplastyballoon for its expansion.

In still yet another embodiment of the invention, the stent has branchesthat support multiple vessels at a bifurcation.

In still yet another embodiment of the invention, the wall thickness ofthe stent is less than 0.5 mm, and preferably less than 0.25 mm.

In still yet another embodiment of the invention, the stent covering hasdifferent porosities in different regions. In those regions, typicallythe ends, where tissue ingrowth and re-endothelialization are desired,the stent covering is more porous, and in those regions were it isdesirable to inhibit such in growth, the stent covering is substantiallynon-porous.

In still yet another embodiment of the invention, the pore diameter isbetween 30 to 120 micrometers.

In still yet another embodiment of the invention, the distance betweenthe pores is about 3 times the diameter of the pore.

In still yet another embodiment of the invention, the stent has a filterin which the filter membrane is comprised of a fine mesh material thathas a pore size capable of blocking emboli while allowing continuedblood flow.

In still yet another embodiment of the invention, the stent is a stentgraft or intraluminal graft.

In still yet another embodiment the invention is directed to a method offorming a stent. In one such embodiment, a molten piece ofbulk-solidifying amorphous alloy is cast into near-to-net shape for astent component or as a precursor to a stent component. In anotherpreferred embodiment of the invention, a feedstock of bulk-solidifyingamorphous alloy is heated to around the glass transition temperature andformed into a near-to-net shape component for a stent or as a precursorto a stent component.

In still yet another embodiment of the invention, the surface of thestent is modified by chemical treatment. In such an embodiment, thechemical treatment may use a mixed aqueous solution of hydrofluoric acidor nitric acid or sodium hydroxide, or a thermal treatment under in-airoxidation, or a combination of the aforementioned treatments.

In still yet another embodiment, the invention is directed to a methodof duplicating desired morphological features onto the surface of thestent.

In still yet another embodiment of the invention, the fabricationprocess compromises creating a pattern of slots or apertures in aflexible metallic tubular member, by processes including but not limitedto, electrostatic discharge machining (EDM), chemical milling, ablationand laser cutting. These slots or apertures may be cut completely orpartially through the wall of the flexible metallic tubular member.

In still yet another embodiment of the invention, the fabricationprocess compromises a finishing process which includes electro-polishingor chemical etching to provide a highly polished and smoothed surface.

In still yet another embodiment of the invention, the stent strut designprovides for a specific amount of elastic deformation.

In still yet another embodiment of the invention, the stent strut designis such that some strut segments are elastically deformed whencollapsing the stent to a compact size and other strut segments remainundeformed.

In still yet another embodiment of the invention, specific stent strutdesign permits certain segments to be elastically deformed more thanother stent strut segments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 shows a schematic of one embodiment of a stent design accordingto the current invention.

FIG. 2 shows a schematic of a second embodiment of a stent designaccording to the current invention.

FIG. 3 shows a schematic of a third embodiment of a stent designaccording to the current invention.

FIG. 4 shows a schematic of a fourth embodiment of a stent designaccording to the current invention.

FIG. 5 shows a flow chart of one exemplary embodiment of a method offorming stents in accordance with the current invention.

FIG. 6 shows a flow chart of another exemplary embodiment of a method offorming stents in accordance with the current invention.

DETAILED DESCRIPTION OF THE INVENTION

The current invention is directed to stents made of bulk-solidifyingamorphous alloys. Stents, in their expanded form, are generally designedto sustain substantial flexural strain in the longitudinal direction,and ability to carry load in radial direction. Even though,sophisticated designs are utilized to improve such desiredcharacteristics of the stents, the metals and alloys currently used tomanufacture the stents show major shortcomings, especially for thestents of smaller diameter.

Applicants have discovered that bulk-solidifying amorphous alloys havegeneral characteristics, which can be tailored to be particularly usefulin stent applications. These characteristics, as will be shown below,make bulk-solidifying amorphous alloys uniquely suited as a new class ofmaterials for use in stents.

Bulk solidifying amorphous alloys are a recently discovered family ofamorphous alloys, which can be cooled at substantially lower coolingrates, of about 500 K/sec or less, and substantially retain theiramorphous atomic structure. As such, these materials can be produced inthickness of 1.0 mm or more, substantially thicker than conventionalamorphous alloys of typically 0.020 mm which require cooling rates of10⁵ K/sec or more. Furthermore, these alloys are capable of showingglass transition and form an extended super-cooled liquid regime beforethe onset of the crystallization. For example, these alloys havetypically a ΔT (temperature range between the glass transition and theonset of crystallization) of 50° C. or more and up to 100° or more forspecific compositions. As such they can be deformed to significantextent with ease under very small stress. Furthermore, bulk-solifyingamorphous alloys have high yield strength and good corrosion resistance.Exemplary alloy materials are described in U.S. Pat. Nos. 5,288,344;5,368,659; 5,618,359; and 5,735,975 (the disclosures of which areincorporated in their entirety herein by reference).

One exemplary family of bulk solidifying amorphous alloys can bedescribed as (Zr,Ti)_(a)(Ni,Cu, Fe)_(b)(Be,Al,Si,B)_(c), where a is inthe range of from 30 to 75, b is in the range of from 5 to 60, and c inthe range of from 0 to 50 in atomic percentages. Furthermore, thosealloys can accommodate substantial amounts of other transition metals upto 20% atomic, and more preferably metals such as Nb, Cr, V, Co, Ta, Mo,W. A preferable alloy family is (Zr,Ti)_(a)(Ni,Cu)_(b)(Be)_(c), where ais in the range of from 40 to 75, b is in the range of from 5 to 50, andc in the range of from 5 to 50 in atomic percentages. Still, a morepreferable composition is (Zr,Ti)_(a)(Ni,Cu)_(b)(Be)_(c), where a is inthe range of from 45 to 65, b is in the range of from 7.5 to 35, and cin the range of from 10 to 37.5 in atomic percentages. Anotherpreferable alloy family is (Zr)_(a)(Nb,Ti)_(b)(Ni,Cu)_(c)(Al)_(d), wherea is in the range of from 45 to 65, b is in the range of from 0 to 10, cis in the range of from 20 to 40 and d in the range of from 7.5 to 15 inatomic percentages. These bulk-solidifying amorphous alloys can sustainstrains up to 1.5% or more and generally around 1.8% without anypermanent deformation or breakage. The yield strength of bulksolidifying alloys range from 1.6 GPa and reach up to 2.5 GPa and moreexceeding the current state of the Titanium alloys.

Another set of bulk-solidifying amorphous alloys are ferrous metals (Fe,Ni, Co) based compositions. Examples of such compositions are disclosedin U.S. Pat. No. 6,325,868; (A. Inoue et. al., Appl. Phys. Lett., Volume71, p 464 (1997); (Shen et. al., Mater. Trans., JIM, Volume 42, p 2136(2001)); and Japanese patent application 2000126277 (Publ. #0.2001303218A), all of which are incorporated herein by reference. One exemplarycomposition of such alloys is Fe₇₂Al₅Ga₂P₁₁C₆B₄. Another exemplarycomposition of such alloys is Fe₇₂Al₇Zr₁₀Mo₅W₂B₁₅. Although, these alloycompositions are not processable to the degree of the above-citedZr-base alloy systems, they can still be processed in thicknesses around1.0 mm or more, sufficient enough to be utilized in the currentinvention. Similarly, these materials have elastic strain limits higherthan 1.2% and generally around 1.8%. The yield strength of theseferrous-based bulk-solidifying amorphous alloys is also higher than theZr-based alloys, ranging from 2.5 GPa to 4 GPa, or more.

In general, crystalline precipitates in bulk amorphous alloys are highlydetrimental to the properties of bulk-solidifying amorphous alloys,especially to the toughness and strength of these materials, and, assuch, such precipitates are generally kept to as small a volume fractionas possible. However, there are cases in which, ductile crystallinephases precipitate in-situ during the processing of bulk amorphousalloys, are indeed beneficial to the properties of bulk amorphousalloys, and especially to the toughness and ductility of the materials.Such bulk amorphous alloys comprising such beneficial precipitates arealso included in the current invention. An exemplary composition of suchalloy is Zr_(56.2)Ti_(13.8)Nb_(5.0)Cu_(6.9)Ni_(5.6)Be_(12.5) in atomicpercentages. This alloy has a low elastic modulus of from 70 GPa to 80GPa depending on the specific microstructure of ductile-crystallineprecipitates. Further, the elastic strain limit is 1.8% or more and theyield strength is 1.4 GPa and more.

Although a number of bulk solidifying amorphous alloy compositions aredescribed above, the alloy can also be preferably selected to be free ofNi or Al or Be in order to address high sensitivity or allergy ofspecific population groups to such metals.

The unique advantage of utilizing bulk solidifying amorphous alloys isnot a single specific property, but rather the simultaneous existence ofa set of properties. Furthermore, these properties can be obtained invarious design packages with a high degree of fabricability, especiallyfor the components of small dimensions as found in stents. As such,these alloys show their advantage best in smaller stent dimensions suchas for the stents of 6.0 mm or less in diameter, and especially for thestents of under 3.0 mm in diameter.

First of all, bulk-solidifying amorphous alloys have typically 50% ormuch more higher yield strength than conventional alloys of itsconstituent elements. For example, a titanium base crystalline alloy(such as Ti-6-4) has a yield strength typically around 850 MPa, whereasTi-base amorphous alloys have a yield strength around 1900 Mpa andhigher. Secondly, bulk solidifying amorphous alloys have a very highelastic strain limit, which characterizes a material's ability tosustain strains without permanent deformation. Typicallybulk-solidifying amorphous alloys have elastic strain limits of around1.8% or higher. The combination of very high yield strength and veryhigh elastic strain limit provides a unique advantage of designingstents with high load carrying ability in radial directions andmeanwhile sustain very high flexural strains in longitudinal directions.

In a typical stent application in the body, stents are inserted in avery compact package to facilitate the aiding of insertion and movementto the desired position in the vessel. Then, the stent is expanded intoits operational shape in two distinct methods. In the first method,generally used for stainless steel or pure titanium, the stent isplastically deformed into its operational shape by means of anangioplasty balloon. In the other method, generally reserved forshape-memory alloys such as Nitinol, the stent expands by the aid ofself “memory energy” put into the stent package utilizing the shapememory effect of specific phase transformation property for thesealloys. The latter stents are called self-expanding and preferred due tosuch ability, which eliminates the need for operation of a separateangioplasty balloon to expand the stent.

In either case, the yield strength of stent material is generally under1 GPa. Accordingly, the stents are made with larger wall-thickness toprovide resistance and load carrying ability in radial directions sothat restenosis forces from the vessel can be counteracted. However,this is not desirable, as the stent will have a high form factor (theform factor is defined for the radial direction as the ratio of the areaof open space (scaffolded area) to the area covered by stent wallthickness). Generally, for stent diameters of 3.0 mm or less, thisbecomes a more critical issue that, where the form factor of stentbecomes unacceptable for practice when conventional stent metals andalloys are used. Even though, there exists some metals and alloys withvery high yield strengths exceeding 1 GPa, (such as maraging steel),these alloys are not deemed useful due to fabricability issues incomplex and small geometries, as well as corrosion and bio-compatibilityissues. Furthermore, such alloys provide major problems in packagingstents into compact shapes for delivery since they do not haveshape-memory

The use of bulk-solidifying amorphous alloys allows the production ofstents with a smaller form factor (utilizing the higher yield strengthof bulk-solidifying amorphous alloys), and a packaging method utilizingthe truly mechanical elastic behavior of the material. For example, thehigher yield strength of bulk-solidifying amorphous alloys can beutilized to make stents with smaller wall thicknesses, while maintainingan acceptable radial structural integrity. Meanwhile, this smaller wallthickness can be beneficially utilized, in turn, to facilitate a stentstructure that is more flexible in a longitudinal direction.Furthermore, the smaller wall thickness greatly facilitates thepackaging of stents into a compact geometry, as such, various prior artstent designs can be more effectively utilized. For example, FIG. 1 to 4show a variety of exemplary conventional stent designs that might beformed using a bulk-solidifying amorphous alloy according to the presentinvention including: mesh designs, as shown in FIGS. 1 and 2, andnon-mesh designs, such as helical coils and rolls as shown in FIGS. 3and 4.

Moreover, new novel stent designs can be developed to readdress oldapplications and to newly address new stent applications and designs.For example, FIG. 4 shows a collapsed stent with locking mechanisms 10and 11, which when expanded interlock to maintain the desired shape ofstent. In addition, to more complicated stent designs, these properties,along with the added benefit of various fabrication methods unique tobulk-solidifying amorphous alloys, makes the development of stents withdiameter of under 3.0 mm more feasible.

Accordingly, in one embodiment of the current invention a stent isfabricated from a bulk solidifying amorphous alloy with a yield strengthof at least 1.5 GPa or more, preferably with a yield strength of 2.0 GPaor more, and most preferably with a yield strength of 3.0 GPa or more.Additionally, the bulk solidifying amorphous alloy is selected such thatthe elastic strain limit is 1.5% or higher and more preferably 1.8% orhigher. In the delivery package, the stent is compacted (or compressed)by mechanical forces such that the bulk solidifying amorphous alloys isstrained up to 1.0% or higher, and preferably 1.5% or higher, but notexceeding its elastic strain limit. (Herein, the strain is intended forthe stent material and not the strain of the overall geometry).Subsequent to the stent insertion, the retaining mechanical forces arereleased and the stent self-expands to reduce the strain below 0.5% andpreferably below 0.25%, meanwhile exerting an outward scaffoldingpressure to the vessel.

Although a number of potential bulk-solidifying amorphous alloys arediscussed above, Zr/Ti base bulk-solidifying amorphous are preferred dueto their excellent paramagnetic characteristics (lack of ferromagnetism)and better bio-compatibility. Paramagnetic characteristics are desiredfor MRI (magnetic-resonance imaging) compatibility. Zr-basebulk-solidifying amorphous alloys are further preferred as theygenerally have more robust processability characteristics, which allowsa better ability to form these materials into the necessarysophisticated designs.

Ferrous-base bulk-solidifying amorphous alloys may also be used and arepreferred for their relatively higher yield strength of 3.0 GPa or more.Ferrous alloys are preferably selected such that they have enoughalloying non-magnetic alloying elements to retard the ferro-magneticproperties of Fe and Ni to provide MRI compatibility. One such preferredelement for retarding ferro-magnetism in ferrous alloys is Manganese.Another preferred element is Copper. Zr and Ti can also be utilizedeffectively as alloying additions to retard ferro-magentism in suchferrous base alloys, provided sufficient leeway is given to preserve theability of bulk-solidification of the final alloy into an amorphousstructure.

Another important characteristic, which can be tailored with using bulksolidifying amorphous alloys, is radio-opacity. This is highly desirableduring the application or placement of a stent in order to locate stentlocation and length more precisely using fluorescence imaging. Zr-basebulk-solidifying amorphous alloys are preferred for better radio-opacitythan Ti-base alloys. Further, elements of high atomic numbers, such asTa, Hf, W can be quite readily added as alloying additions into Zr—Tibase alloys for improved radio-opacity. Furthermore, these elements (Hf,Ta, W) of high atomic number can further be used as partial replacementsfor lower atomic number elements such as Zr, Nb, and Mo, respectively,to provide better radio-opacity. Pd can also be used as a replacementfor Ni or Co to improve radio-opacity. Due to the unique atomicstructure, such alloying additions and/or replacements can be morereadily used in bulk solidifying amorphous alloys, without sacrificingother beneficial properties mentioned above, unlike conventional metalsand alloys.

It is also possible to form micro-structured surface morphologies bydesign using bulk-solidifying amorphous alloys. Such microstructures canbe in the shape of pores, which, for example, aid drug coating andcarrying. Herein, the pores are differentiated from slots and aperturesand are rather defined as surface depressions and do not necessarilypass all the way through the wall thickness of the stent. The uniqueamorphous atomic microstructure of these materials responds uniformly tothe forming operations of micron and sub-micron scales making itpossible to form features within the desirable morphological ranges.This is in distinct contrast to conventional metals and alloys, wherethe microstructure of the material is characterized by crystallites(individual grains typically with dimensions of few to several hundredsmicrons), each of which has different crystallographic orientation and,as such, responds non-uniformly to shaping and forming operations.

The micro-structured surface morphology according to the currentinvention can be produced in two alternative ways. In a first exemplarymethod, as outlined in FIG. 5, the surface morphology can besimultaneously formed during the fabrication of stent components bycasting methods. In such an embodiment the mold surfaces used in thecasting operation can be pre-configured to have the negative impressionof the desired surface microstructure so that the bulk-solidifyingamorphous alloy replicates such features upon casting. The relativelylow melting temperature of bulk-solidifying amorphous alloys and thelack of any first-order phase transformation during the solidificationreadily enables the replication of micron sized mold features during thecasting of the stent components. Such a process is highly desirable asseveral steps of post-finishing and surface preparation operations canbe reduced or eliminated.

In an alternative exemplary method, as outlined in FIG. 6, apre-fabricated stent component made of bulk-solidifying amorphous alloyis subjected to a surface micro-structuring process at around the glasstransition temperature of the bulk-solidifying amorphous alloy material.In such an embodiment, the fabricated stent component is heated toaround the glass transition temperature and pressed against a moldhaving the negative impression of the desired surface microstructure. Asthe bulk solidifying amorphous alloy will readily transition into aviscous liquid regime upon heating, the replication of the desiredsurface morphology can readily take place. In this embodiment of themethod, bulk-solidifying amorphous alloys with a large ΔTsc (supercooledliquid region) is preferred. Bulk-solidifying amorphous alloys with aΔTsc of more than 60° C., and still more preferably a ΔTsc of 90° C. andmore are desired for a high-definition surface micro-structuring. Oneexemplary of such alloy having ΔTsc of more than 90° C. isZr₄₇Ti₈Ni₁₀Cu_(7.5)Be_(27.5). (ΔTsc is defined as the difference betweenTx (the onset temperature of crystallization) and Tsc (the onsettemperature of super-cooled liquid region). These values can beconveniently determined by using standard calorimetric techniques suchas by DSC measurements at 20° C./min).

Once a suitable stent component is fabricated into a near-net shape,further fabrication processes such as electrostatic discharge machining(EDM), chemical milling, ablation, and laser cutting can be utilized tocut slots or apertures completely or partially through the wall of theflexible metallic tubular member. Such processes, when properly applied,will not have any significant effect on the above mentioned beneficialmechanical properties. Furthermore, final-finishing operations such aselectro-polishing or chemical etching as well as anodizing can beapplied to provide a highly polished and smoothed surface. Suchprocesses have added advantage in the bulk solidifying amorphous alloysthat, the uniformity of the microstructure to the atomic level willfacilitate the effective use of such operations without any suchdeficiencies which are found in crystalline alloys due to crystallinedirections and preferential etching.

Finally, various casting processes, such as metal mold casting andinvestment casting can be utilized to fabricate stent components ofbulk-solidifying amorphous alloys employing sufficiently fast coolingrates. Small form-factor tubular stent members can be readily producedwith very high yield strengths of 1.5 Gpa and higher. Furthermore,utilizing processes such as investment casting, highly intricate andcustomized stent components can be cast. Such as-cast components willhave a very high yield strength exceeding 1.5 Gpa and an exceptionallyhigh elastic strain limit of 1.5% or higher without any subsequentthermo-mechanical processes or heat treatment.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention.

1. A stent of a radially compactable generally tubular body comprising abulk-solidifying amorphous alloy, wherein the alloy is subjected to anelastic strain of at least 1.0% in a compacted form of the stent.
 2. Thestent described in claim 1, wherein the amorphous alloy has an elasticstrain of at least 1.5%.
 3. The stent described in claim 1, wherein theamorphous alloy has an elastic strain of at least 1.5%, and a yieldstrength of more than 1.4 Gpa.
 4. The stent described in claim 1,wherein the amorphous alloy has an elastic strain of at least 1.8%, anda yield strength of more than 1.9 Gpa.
 5. The stent described in claim1, wherein the amorphous alloy is subjected to an elastic strain of atleast 1.5% in a compacted form of the stent.
 6. The stent described inclaim 1, wherein the amorphous alloy is subjected to an elastic strainof at least 1.8% in a compacted form of the stent.
 7. The stentdescribed in claim 1, wherein the amorphous alloy is subjected to anelastic strain of less than 0.5% in an expanded form of the stent. 8.The stent described in claim 1, wherein the amorphous alloy has a deltaT of greater than 90° C.
 9. The stent described in claim 1, wherein theamorphous alloy is a Zr/Ti base bulk-solidifying amorphous alloy. 10.The stent described in claim 1, wherein the stent has a cross-sectionselected from the group consisting of hexagonal and round.
 11. The stentdescribed in claim 1, wherein the body comprises a plurality of piecesarranged in a conformation selected from the group consisting of coiledspring, helical wound spring coil, zigzag pattern, diamond shaped, andnon-mesh designs.
 12. The stent described in claim 1, wherein the wallof the body has a plurality of aperture openings.
 13. The stentdescribed in claim 1, wherein the body covers between 9 and 20% of avessel into which the stent is implanted.
 14. The stent described inclaim 1, wherein the body covers at least 80% of a vessel into which thestent is implanted.
 15. The stent described in claim 1, wherein the bodycomprises at least two tubular segments which overlap or abut to form asingle tubular body.
 16. The stent described in claim 1, wherein thestent is self-expanding.
 17. The stent described in claim 1, wherein thebody is branched.
 18. The stent described in claim 1, wherein the bodyhas a wall thickness of less than 0.5 mm.
 19. The stent described inclaim 1, wherein the body has a wall thickness of less than 0.25 mm. 20.The stent described in claim 1, wherein the stent is one of either astent graft or intraluminal graft.
 21. A method of forming a stent,comprising: providing a molten piece of bulk-solidifying amorphousalloy; providing a mold in the shape of a desired stent component;casting the molten amorphous alloy into a plurality of near-to-net shapestent components; assembling a stent from the stent components; andcompacting the stent radially to form a compacted stent, wherein theamorphous alloy piece is subjected to an elastic strain of at least 1.0%during compacting.
 22. The method as described in claim 21, furthercomprising finishing an outer surface the stent, wherein the finishingis selected from a process selected from the group consisting ofelectro-polishing and chemical etching.
 23. The method as described inclaim 21, further comprising modifying an outer surface of the stent bya treatment selected from the group consisting of chemical treatment,thermal treatment, and a combination thereof.
 24. A method of forming astent, comprising: providing a feedstock a bulk-solidifying amorphousalloy; heating the feedstock to around the glass transition temperatureof the amorphous alloy; providing a mold in the shape of a desired stentcomponent; molding the molten amorphous alloy into a plurality ofnear-to-net shape stent components; assembling a stent from the stentcomponents; and compacting the stent radially to form a compacted stent,wherein the amorphous alloy piece is subjected to an elastic strain ofat least 1.0% during compacting.
 25. The method as described in claim24, further comprising finishing an outer surface the stent, wherein thefinishing is selected from a process selected from the group consistingof electro-polishing and chemical etching.
 26. The method as describedin claim 24, further comprising modifying an outer surface of the stentby a treatment selected from the group consisting of chemical treatment,thermal treatment, and a combination thereof.
 27. A method of forming astent comprising: providing a tubular body made of a bulk-solidifyingamorphous alloy; processing the tubular body to form a pattern ofsurface features therein, wherein the surface features extend at leastpartially through the wall of the body; and compacting the stentradially to form a compacted stent, wherein the amorphous alloy issubjected to an elastic strain of at least 1.0% during compacting. 28.The method as described in claim 27, wherein the processing includes amanufacturing method selected from the group consisting of electrostaticdischarge machining (EDM), chemical milling, ablation and laser cutting.29. The method as described in claim 27, further comprising finishing anouter surface the stent, wherein the finishing is selected from aprocess selected from the group consisting of electro-polishing andchemical etching.
 30. The method as described in claim 27, furthercomprising modifying an outer surface of the stent by a treatmentselected from the group consisting of chemical treatment, thermaltreatment, and a combination thereof.